Plastic component subjected to friction

ABSTRACT

A frictionally stressed plastic component, particularly an elastomer component, includes microcapsules which, when damaged, release at least one tribologically effective content substance.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a frictionally stressed plastic component. Apreferred field of application are frictionally stressed seals, bearingsand guiding elements made of plastic material.

In many applications, good frictional characteristics and a low wear aredemanded of plastic components in order to ensure a durability of thecomponents which is as high as possible. For improving the tribologicalcharacteristics, it is known to embed dry lubricants, such as MoS₂ orgraphite, into the plastic materials. These are released during theabrasive wear of the plastic component and develop theirfriction-reducing and wear-reducing characteristic.

It is a disadvantage of this solution that only dry lubricants can beentered into the plastic materials. This considerably restricts theselection of usable lubricants. The use of lubricants which are not dryand particularly liquid lubricants is therefore completely eliminated.As a result, the selection of an optimal combination of lubricant andfrictional partners is not permitted.

Another disadvantage of the above-mentioned solution is the fact thatthe dry lubricants enclosed as particles in the plastic material areheld only mechanically in the plastic material environment. If theadjacent plastic material environment is partially removed by friction,a corresponding opening is created on the side facing the frictionpartner. Through this opening, the particles can leave the plasticmaterial as well as the interactional area without carrying out theirdesired function. This is particularly disadvantageous if the frictionpartners are additionally protected from friction and wear by means of aliquid lubricant. In this case, the dry lubricant can easily be absorbedby the liquid lubricant and may be removed by it from the tribologicallystressed area without developing its effect. This is particularly truewhen the liquid lubricant is additionally subjected to a revolution.

Another considerable disadvantage of the above-mentioned solutionconsists of the fact that the mechanical building-in of dry lubricantsdisadvantageously changes the mechanical characteristics of the plasticcomponent. Thus, the components may become brittle, lose stability, orthe resistance to temperature changes may be impaired. Particularly inthe case of elastomer components, as a rule, the modulus of elasticityis reduced and, as a result, the deformation characteristics areimpaired which can lead to a malfunctioning of the component, forexample, leakages at sealing surfaces.

The invention is based on the technical problem of providingfrictionally stressed plastic components into which arbitrarytribologically effective content substances can be built. The inclusionof the content substances in the plastic component should take place notonly mechanically but, on the contrary, by chemical linkages with theplastic material. Also, the mechanical characteristics of the plasticstarting material, and particularly its elasticity, should not bechanged.

According to the invention, it is recognized that these problems will besolved by a plastic component, particularly an elastomer component. Thiselastomer component contains microcapsules, which in the event of theirfrictionally caused damaging, release at least one tribologicallyeffective content substance that develops the desired friction-reducingand wear-reducing effect.

DETAILED DESCRIPTION OF THE INVENTION

The production of the microcapsules is generally known. Themicrocapsules are added to the plastic mass before the shaping of theplastic material and consist of a membrane shell and the contentsubstances or filling substances enclosed therein. Shell materials aswell as filling materials may consist of many different substances.

The used plastic material can be selected arbitrarily in the sense ofthe invention. Duroplastics or thermoplastics, for example, aresuitable. Plastic materials, which are particularly suitable because oftheir elasticity, are elastomers, for example, those produced byinjection molding.

As a result of a suitable selection of the shell material, an adaptationto the matrix material and the processing conditions can be ensured.Such an adaptation is generally known on the basis of its principles.The adaptation to the shell material is carried out such that the shellmaterial enters chemical linkages with the plastic matrix. As a resultof the chemical linkages, the microcapsules are fixedly connected withthe matrix and a purely mechanical embedding as in the case of the drylubricant particles according to the prior art is avoided. Thus, it isexcluded that the microcapsule leaves the tribologically stressed areawithout any pouring-out of the content substance.

For the above-mentioned adaptation, it is advantageous for the membraneshell to also consist of a plastic material which, in addition, is notattacked by the content substance or substances. Content substancessuitable for this purpose may be liquid or solid. Particularly, oils andgreases are suitable for many applications, but also dry lubricants,such as MOS₂, TEFLON or graphite. By accommodating the contentsubstances in microcapsules, a very large number of tribologicallyeffective content substances are available which permit a flexibleadaption of the content substances to the respective application. Thesimultaneous use of microcapsules with different content substances isalso perceivable.

The microcapsules have an essentially round shape and a rather preciselyadjustable diameter of from approximately 0.5 μm to 1,000 μm. Thequantity of content substances in the component can be adjusted withinwide ranges by way of the capsule volume and by way of the volumefraction of the capsules on the component volume. For most applications,a volume fraction of encapsulated content substances of maximally 25% ofthe component volume should be sufficient.

The use of the plastic components according to the invention would beadvantageous wherever plastic materials are tribologically considerablystressed. Examples are seals (such as sealing rings, particularly radialpacking rings), bearings (such as roller bearings and slide bearings)and guiding elements (such as guide rails, guide grooves, guide plates,guide pins). These applications are characterized in that thetribologically stressed points are always subjected to the same frictionpartner, for example, because of periodic mechanical movements of thefriction partners. If the elastic characteristics also matter in theapplications (for example, in the case of seals), a plastic matrix madeof an elastomer would be useful.

For an efficient use of the microencapsulated content substances, it isuseful to arrange microcapsules preferably or even exclusively in thetribologically stressed volume ranges of the component. Particularly inthe case of large parts, the used quantity of microcapsules will thenclearly be smaller, which results in a reduction of costs. Furthermore,the lubricants will emerge only at points at which they are needed.

The locally limited or reinforced installation of microcapsules intothese tribologically stressed volume ranges takes place by suitableinjection methods.

Best Implementation of the Invention

The plastic components according to the invention can advantageously beused in the case of components which consist of several plastic parts,for example, radial packing rings. Such sealing rings usually consist ofelastomers with sealing lips attached by injection molding or gluing andmade of a different material. The second material may, for example, beTEFLON or another wear-proof plastic material. Essentially only thesealing lip is tribologically stressed. In the sense of the invention,the sealing lip may be a microcapsule-containing elastomer, in the caseof which the microcapsules contain a lubricating oil. According to, anembodiment of the present invention, only the volume range of thesealing lip contains microcapsules. The locally desired surfacecharacteristics can therefore be implemented without changing theoverall component characteristics.

What is claimed is:
 1. A frictionally stressed component comprising: aninjection molded elastomer; and a plurality of microcapsules that, whendamaged, release at least one tribologically effective contentsubstance.
 2. A component according to claim 1, wherein the contentsubstance is an oil, a grease, or a solid lubricant.
 3. A componentaccording to claim 1, wherein the microcapsules have a plastic membrane.4. A component according to claim 1, wherein the microcapsules have adiameter in the range of between 0.5 μm and 1,000 μm.
 5. A componentaccording to claim 1, wherein the encapsulated content substance has avolume fraction that is a maximum of 25% of the component volume.
 6. Acomponent according to claim 1, wherein the microcapsules are intribologically stressed regions of the component.
 7. A componentaccording to claim 1, wherein the microcapsules are present only in thetribologically stressed regions of the component.
 8. A componentaccording to claim 1, wherein said component is a seal, a bearing, or aguiding element.